1. Field of the Invention
The present invention relates to an organic light emitting diode (OLED) display device and a method of manufacturing the same, and more particularly, to an OLED display device with high resolution and a method of manufacturing the same.
2. Discussion of the Related Art
With the advance of information display devices that are light and have excellent portability, the advance of the information society is accelerating. As a representative type of flat panel display device that is thin in thickness, liquid crystal display (LCD) devices were already commercialized and replaced cathode ray tube (CRT) display devices, and OLED display devices are attracting much attention as next generation flat panel display devices. Since the OLED display devices do not use a separate light source such as a backlight applied to the LCD devices, the OLED display devices have a thin thickness and a good color reproduction rate compared to the LCD devices, thus realizing a sharp image. Also, the OLED display devices have a wide viewing angle, a good contrast ratio, a fast response time, and low power consumption.
FIG. 1 is a sectional view illustrating a portion of a related art OLED display device.
As illustrated in FIG. 1, the related art OLED display device includes a substrate 110, a thin film transistor Tr, a first storage electrode 122, a second storage electrode 133, a planarization layer 140, an anode electrode 150, and a bank layer 160.
First, the thin film transistor Tr is formed on the substrate 110. The thin film transistor Tr includes a semiconductor layer 111, a first gate insulating layer 120, a gate electrode 121, a second gate insulating layer 130, a source electrode 131, and a drain electrode 132.
The semiconductor layer 111 and the first gate insulating layer 120 are sequentially formed on the substrate 110, and the gate electrode 121 is formed on the semiconductor layer 111. The first storage electrode 122 and the gate electrode 121 are simultaneously formed on the first gate insulting layer 120, namely, on the same layer. The second gate insulating layer 130 insulating the gate electrode 121 is formed on the gate electrode 121. A plurality of contact holes are formed in the first and second gate insulating layers 120 and 130 to partially expose the semiconductor layer 111, and then the source electrode 131 and drain electrode 132 respectively connected to the exposed portions of the semiconductor layer 111 are formed on the second gate insulating layer 130, namely, on the same layer. Also, the second storage electrode 133 is formed in an area corresponding to the first storage electrode 122 simultaneously with the source electrode 131 and the drain electrode 132. Subsequently, the anode electrode 150 connected to the drain electrode 132 is formed, and the bank layer 160 defining a contact area (i.e., an emitting area) between the anode electrode 150 and the organic emitting layer (not shown) is formed.
In this case, the first storage electrode 122 formed simultaneously with the gate electrode 121 and the second storage electrode 133 formed simultaneously with the source electrode 131 and drain electrode 132 generate a capacitance, thereby enabling the organic emitting layer to hold a light emitting state during one frame. However, the first storage electrode 122 may be replaced by doping the semiconductor layer 111. Also, the above-described example uses a top gate type, but the storage electrodes Cst may be formed in the same type independent of various types, such as a bottom gate type or a double gate type, of the thin film transistor Tr.
Since the storage electrodes Cst of the related art OLED display device are all formed simultaneously with some elements of the thin film transistor Tr, the storage electrodes Cst are restrictively formed in only an area, in which the thin film transistor Tr is not formed, in a pixel area. In this case, a design freedom of the storage electrode Cst is reduced by the thin film transistor Tr. Furthermore, the storage electrode Cst should be formed to have a certain area or more for generating a certain capacitance that holds a light emitting state of the organic emitting layer during one frame. Therefore, a pixel size is inevitably enlarged for forming the storage electrode Cst (limited in design freedom) occupying a certain area or more, causing a reduction in resolution.